1. Field of the Invention
The present invention relates to a diaphragm pump with two diaphragms disposed in a pump housing which act on a fluid medium to be pumped, e.g. a paint, which diaphragms can be actuated by means of an adjusting piston arranged in between the diaphragms upon both sides of which a pressurized medium can act alternately and which diaphragms are supported in the terminal areas of two piston rods that are firmly connected to the adjusting piston.
2. Description of the Prior Art:
A diaphragm pump of this type is disclosed in DE 195 35 745 C1. In this embodiment, a further pressure space is assigned to each of the two diaphragms and the pressure spaces are separated from the pumping spaces by the diaphragms. In this case, pressurized medium is supplied in a controlled fashion to the pressure spaces synchronously to the adjustment movements of the drive piston of a pneumatic motor that is mechanically connected to the diaphragms, with the effect that although a pressure ratio is achieved, the complexity of the construction and the level of the investment required are both considerable.
This is because a separate control device is provided in between the pneumatic motor and one of the diaphragms, and this control device is susceptible to defects and large in size. However, the principal disadvantage is that each of the diaphragms folds over during the transition from a suction stroke to a pressure stroke and their flexing zones are highly stressed by the alternating tensile and compression loads. This leads to damage to the diaphragms after only a relatively short operating time, meaning that the diaphragms have to be renewed and interruptions in operation have to be accepted in such cases. Furthermore, the folding over of the diaphragms has an unfavorable effect on the pumping behavior of the diaphragm pump because changes in volume in the pumping spaces are unavoidable and the pumping flow pulsates as a result.